HtmlElement.KeyDown 事件

定义

命名空间:

System.Windows.Forms

程序集:

System.Windows.Forms.dll

当用户按下键盘上的某个键时发生。

public:
 event System::Windows::Forms::HtmlElementEventHandler ^ KeyDown;

public event System.Windows.Forms.HtmlElementEventHandler KeyDown;

member this.KeyDown : System.Windows.Forms.HtmlElementEventHandler 

Public Custom Event KeyDown As HtmlElementEventHandler 

事件类型

HtmlElementEventHandler

示例

下面的代码示例演示了此成员的用法。 在此示例中，事件处理程序报告事件的发生情况 KeyDown 。 此报表可帮助你了解事件发生的时间，并可以帮助你进行调试。 若要报告多个事件或频繁发生的事件，请考虑将 MessageBox.Show 替换为 Console.WriteLine 或将消息追加到多行 TextBox。

若要运行示例代码，请将其粘贴到包含名为 HtmlElement1的 类型的HtmlElement实例的项目中。 然后，确保事件处理程序与 KeyDown 事件相关联。

private void HtmlElement1_KeyDown(Object sender, HtmlElementEventArgs e) {

System.Text.StringBuilder messageBoxCS = new System.Text.StringBuilder();
messageBoxCS.AppendFormat("{0} = {1}", "MouseButtonsPressed", e.MouseButtonsPressed );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "ClientMousePosition", e.ClientMousePosition );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "OffsetMousePosition", e.OffsetMousePosition );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "MousePosition", e.MousePosition );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "BubbleEvent", e.BubbleEvent );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "KeyPressedCode", e.KeyPressedCode );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "AltKeyPressed", e.AltKeyPressed );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "CtrlKeyPressed", e.CtrlKeyPressed );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "ShiftKeyPressed", e.ShiftKeyPressed );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "EventType", e.EventType );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "ReturnValue", e.ReturnValue );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "FromElement", e.FromElement );
messageBoxCS.AppendLine();
messageBoxCS.AppendFormat("{0} = {1}", "ToElement", e.ToElement );
messageBoxCS.AppendLine();
MessageBox.Show(messageBoxCS.ToString(), "KeyDown Event" );
}

Private Sub HtmlElement1_KeyDown(sender as Object, e as HtmlElementEventArgs) _ 
     Handles HtmlElement1.KeyDown

    Dim messageBoxVB as New System.Text.StringBuilder()
    messageBoxVB.AppendFormat("{0} = {1}", "MouseButtonsPressed", e.MouseButtonsPressed)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "ClientMousePosition", e.ClientMousePosition)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "OffsetMousePosition", e.OffsetMousePosition)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "MousePosition", e.MousePosition)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "BubbleEvent", e.BubbleEvent)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "KeyPressedCode", e.KeyPressedCode)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "AltKeyPressed", e.AltKeyPressed)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "CtrlKeyPressed", e.CtrlKeyPressed)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "ShiftKeyPressed", e.ShiftKeyPressed)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "EventType", e.EventType)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "ReturnValue", e.ReturnValue)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "FromElement", e.FromElement)
    messageBoxVB.AppendLine()
    messageBoxVB.AppendFormat("{0} = {1}", "ToElement", e.ToElement)
    messageBoxVB.AppendLine()
    MessageBox.Show(messageBoxVB.ToString(),"KeyDown Event")

End Sub

注解

KeyDown 发生在 之前 KeyPress，后者又发生在 之前 KeyUp。

通过将 类true的 HtmlElementEventArgs 属性设置为 ReturnValue ，可以取消元素上事件的默认操作KeyDown。

KeyDown元素上的事件也会在该元素的父元素和类本身上HtmlDocument发生，除非将 类的 HtmlElementEventArgs 属性设置为 BubbleEventtrue。

另请参阅

• onkeydown 事件